Not entirely sure I understand the question, but you need a way to make a bunch of files into a bootable windows xp iso right? Use nlite for that purpose - it can alter the content of the xp as well, and can burn directly to disk. Not tried it in windows 8, but I assume you'll need to run it as admin to get access to the dvd burning feature (I had to do that with another iso burner in server 2012 at least)